We have covered various methods of avoiding the bogeyman of email marketing: spam filters. Don’t stop reading when I say that no one can be definitive. Everyone, and that includes me, is guessing to an extent. Experience helps, but when it starts to become useful, they change the rules.
We can deduce some of the parameters though. For instance, there was a suggestion that spam filters favour html over plain text, and to an extent this is true. The reasoning is subtle however. There is more information available to the filtering agent with html, and if they discover just one trigger they might be a bit flexible if all else is reasonable.
Plain text emails give little away and one problematic word can be a disaster as the filter has little else to go on. Previous history will be a significant factor so if you wish to use plain text habitually then every word is vital. Html gives us a bit more freedom of action.
Filters tend to prefer a surfeit of information to work on. Sending an email full of clickable links will generally get you classed as spam, but there is no definitive ratio. The price of the free email marketing templates should not put you off. They provide a guide to what is acceptable.
Another factor is to ensure that links have reputable destinations. Whilst one or two doubtful ones will normally not get you diverted, too many will. Whilst there is no proscribed limit, the fewer the better is the best route.
You can see that reasons for diversion are far from straightforward. A general guideline is that if it will irritate your customers, it will irritate the spam filter.
As a writer it hurts me to say this, but text is included in marketing emails mainly to ensure it is not classed as spam. The preferred ratio is open to argument, but I’d suggest 70% text to 30% images by area is safe. Others, perhaps not writers, suggest 60:40. If all else is strong, then 50:50 will probably not be a problem, but it would be a risk. It would appear that text in an image can cause a problem or worse still, a hidden button.
Let’s put in another plug for email marketing templates. For reasons which are not confirmed, or even perhaps apparent, ISPs like them. They use them as a means of identifying you. This can be a bad thing if you are a spammer of course, so a good thing for us.
This leads us on to another restriction. ISPs and filters don’t like surprises. You wouldn’t expect them to be happy if you crept up behind them and said ‘Boo’, so a sudden change, especially of a From address, or even a change of style, can be problematical, especially for those new to email marketing.
It seems that well established companies test the limits more readily and yet still get through. Herein is the main factor in deliverability. Reputation and trust, especially built up over time, are more important than not using caps in your Subject Line.